1. Field of the Invention
This invention relates to spongeable silicone rubber compositions, a method of making the silicone rubber sponge and a sponge prepared thereby.
2. Description of the Prior Art
The use of 4,4'-oxybis(benzenesulfonhydrazide) as a blowing agent in rubbers is known in the art, as shown by U.S. Pat. No. 2,951,819 which describes both natural and synthetic rubbers which contain stearic acid, being blown with a number of blowing agents including 4,4'-oxybis(benzenesulfonhydrazide). Silicone rubber is described by this patent as one of the synthetic rubbers. This patent does not suggest what might happen upon heat aging of silicone rubber using 4,4'-oxybis(benzenesulfonhydrazide) as the blowing agent. The applicants found that when this compound was used as a blowing agent in silicone rubber, a sponge formed but became brittle upon heat aging.